It is known that Zener diodes of low nominal Zener voltages have a rounded elbow and a comparatively high dynamic resistance (.DELTA.U/.DELTA.I) in the working range of the characteristic.
This shortcoming, i.e., high dynamic resistance increases appreciably with the lower Zener voltages such that at low voltages such as 1 volt, Zener diodes can hardly or not at all be utilized in their basic function as voltage limiters.